During operation of some systems, such as aircraft engine systems, high pressure fluid is generated in one portion of the system and transferred through one or more conduits for use in other portions of the system. The high pressure fluid, which can be a gas such as air, is frequently useful at lower pressures than that at which it is generated. Commonly, the portions of the system using the lower-pressure fluid perform with decreased effectiveness or efficiency if supplied with fluid at the higher, generated pressure. For this reason, pressure regulators or other devices are frequently used to adjust the pressure of the fluid supplied to the low-pressure portions of the system.
Shutoff valves are commonly used to prevent high-pressure fluid from unexpectedly entering low-pressure systems. Typically, such valves operate in an open position, and close in response to detection of presence of fluid pressure above a predetermined value. Such shutoff valves have inherent complications which may hinder their performance. For example, a failure to accurately detect unacceptably high fluid pressure can cause the shutoff valve to remain open when it should be closed. Additionally, actuators operating the shutoff valves may fail to adjust the valve to a closed position at a critical time. Moreover, when a shutoff valve correctly operates, some high pressure fluid has already entered the low pressure portions of the system. With the valve closed, in some cases, the high pressure fluid is retained in the low pressure system, which is undesirable. Finally, when the pressure in the fluid decreases to an acceptable level, the shutoff valve may remain in the closed position and require external intervention to reopen it. Together with the previous possible complications, it is possible for a shutoff valve to remain in a closed position when it should be open, inhibiting fluid from flowing when it should.